Olefin production



Sept' 17, 1958 HUTsoN, y.JR 3,402,216

OI'JEFIN PRODUCT I ON Sept. 17, 1968 Ty HUTSN, .IR I 3,402,216

OLEFIN PRODUCTION GLEFIN PRODUCTION Thomas Hutson, Jr., Bartlesville,Ghia., assignor to Phillips Petroleum Company, a corporation of DelawareContinuation-impart of application Ser. No. 545,092, Apr. 25, 1966. Thisapplication Dec. 27, 1966, Ser. No. 605,047

3 Claims. (Cl. 2MB-633.2)

ABSTRACT F THE DISCLOSURE Saturated alicyclic hydrocarbons are convertedto selected olens with high selectivity by photochlorinating saidhydrocarbons, dehydrochlorinating the resultant monochlorinatedhydrocarbons to produce monooleiins, recovering the selected monoolefinsand recycling the remaining monoolens to extinction throughisomerization to convert the same to the selected monoolen.

This application is a continuation-in-part of my copending applicationSer. No. 545,092, filed Apr. 25, 1966.

This invention relates to the production of olefins. In one aspect,hydrocarbons are photochlorinated, dehydrohalogenated and isomerized toform selected olens. In another aspect, saturated hydrocarbons arephotochlorinated and dehydrohalogenated and the resultant internalolefins are isomerized to form terminal monooleiins. In another aspect,internal olefins areproduced to the exclusion of l-olefin by isomerizingthe l-olens produced by alkyl halide dehydrochlorination. In yet anotheraspect, alkanes having from about 7 to about 15 carbon atoms permolecule are photochlorinated and dehydrohalogenated and the resultantinternal olefins are isomerized to terminal oleiins byhydroborationdisplacement.

Numerous methods have been utilized for the production of olens fromsaturated hydrocarbon compounds. However, the selectivity of theprocesses known in the art tothe production of l-olefins is such thatsubstantial fractionation and recycle operation are required to obtainan economically feasible degree of conversion of feed hydrocarbon to thedesired olefin. As disclosed in said copending application, a higherdegree of selectivity to the required intermediate and end products canbe achieved so that product separation and recycle operations areminimized. Consequently, through the unique combination of highlyefficient chlorination, dehydrochlorination and isomerizationoperations, in addition to the provision for intermediate separation andrecycle, the present invention provides for a process for the productionof 1olefns from saturated hydrocarbons at conversion levels notheretofore obtainable. I have now found that internal olefins cansimilarly be produced to the exclusion of l-olefins thereby providing aprocess of high selectivity and flexibility.

It is therefore an object of this invention to provide for theproduction of olens from saturated hydrocarbon compounds.

It isranother object of this invention to provide for a process andapparatus for the highly specific production of terminal olefins.

t It is another object of this invention to provide for a process andapparatus for the production of either internal or terminal olefins orboth olefins from alkanes in high yields.

Other advantages, objects andaspects of this invention willbe apparentto one skilled in the art in view of the disclosure, drawings and theappended claims.

In accordance with one embodiment of this invention,suitable-hydrocarbon compounds are converted to 1ole.- fins bytheseveral serial st eps ofphotochlorination, de-

nited States Patent hydrochlorination and isomerization. Moreparticularly in accordance with this invention, suitable hydrocarboncompounds are photochlorinated at conditions that enhance theselectivity of the chlorination to thecorresponding monochlorinatedderivatives, the monochlorinated compounds are then dehydrochlorinatedin the presence of a catalyst to form the corresponding monoolefinswhich are subsequently isomerized to convert the internal olefms presentto the corresponding terminal olefin thereby effecting a high degree ofconversion of saturated hydrocarbon feedstock to terminal olefinproduct. Alternatively, internal olefins can be recovered as productfollowing dehydrohalogenation and the l-olen can be isomerized withknown isomerization catalysts to produce internal olefins. In thislatter procedure l-oleiins can be recycled to isomerization to effectessentially complete conversion to internal olefin if desired.

More specifically in accordance with one embodiment of this invention,saturated hydrocarbons are photochlorinated and the reactor eiiluent isfractionated to resolve and recover unreacted feed hydrocarbon andmonoand dichlorinated derivatives. Unreacted hydrocarbon is recycled tothe photochlorination zone, dichlorinated derivatives are removed fromthe system and monochlorinated hydrocarbons are dehydrochlorinated inthe presence of a catalyst to effect a high degree of conversion to thecorresponding oletins. The effluent from the dehydrochlorinationoperation comprising unconverted monochlorinated hydrocarbons, HCl, andinternal and terminal olefins is fractionated to resolve and recover theseveral constituents whereby the unconverted monochlorinatedhydrocarbons are recycled to the dehydrochlorination operation, HCl is'vented from the system, terminal olefin is recovered as product andinternal olen is passed to an isomerization operation wherein it isconverted to the corresponding terminal olefin. The feed from theisomerization operation comprising terminal and internal olen isfractionated to resolve these two constituents whereby the internalolefin is recycled to the isomerization operation and the terminalolefin is recovered as product.

I have also found that considerable advantage and flexibility can beaccomplished by providing the facility in this process for recoveringinternal olefin from the dehydrochlorination operation as product andpassing the 1-olen to a conventional isomerization zone wherein thel-olelin is converted to an equilibrium mixture of internal olefin andl-olen. This mixture can then be fractionated to recover internal olefinas product and 1olefin as recycle to the isomerization zone.

The halogenation and, particularly, the chlorination of hydrocarbons hasbeen accomplished in 'both gaseous and liquid phases by various means.Light and, particularly, ultraviolet light is a known catalyst for thechlorination of paraffin hydrocarbons. However, the production of amonohalogenated 'hydrocarbon without substantial concurrent productionof more highly chlorinated derivatives has been difficult due to thefact that the halogenation reaction occurs stepwise and is not generallyequilibrium limited. Therefore, given sufficient residence time andsuilicient halogen, particularly chlorine, at reaction conditions, thereaction product will contain no monohalogenated derivatives at all. Forthe purposes of the present invention, it is highly desirab'e'to promotethe selective conversion of saturated hydrocarbon feedstock to thecorresponding monohalogenated derivative while substantially limitingconversion to more highly halogenated derivatives. It is thereforepreferred in the process of this invention, to employ as thephotochlorination step the process described in copending Ser. No. 248,543. Briefly, in the process of that invention, a liquid hydrocarbonstream such as n-heptane is treated in several serial photochlorinationzones wherein the hydrocarbon, saturated with halogen, is subjected toultraviolet radiation of sufficient intensity to provide for substantialutilization of the halogen present in each stage. Where chlorine isemployed as the halogen, HC1 is produced in each reactor and is removedfrom the reactor efiiuent by iiashing. The resultant mixture ofunconverted and lhalogenated feed hydrocarbon is contacted withadditional halogen and cooled before exposure to ultraviolet radiationat halogenating conditions in a subsequent photochlorination zonewherein additional conversion to chlorinated hydrocarbon takes place.Through such a mode of operation the reaction temperature is kept lowand the amount of halogen present is maintained considerably below alstoichiometric equivalent which conditions provide for a high degree ofselectivity to the production of monoc'hlorinated derivatives. Theeffiuent from the photochlorination zone is fractionated to recoverunconverted hydrocarbon which is recycled to the photochlorination zone,monochlorinated hydrocarbons which are passed to the subsequentdehydrochlorination operation and more highly halogenated derivativeswhich are removed from the system.

The dehydrohalogenation conditions employed in the process of thisinvention are desirably such that conversion of the chlorinatedhydrocarbons to olefin is accomplished with only a minimum production ofundesirable by-products. It is known that in many cases such reactionscan be thermally initiated. Thus, heating at elevated temperatures isfrequently sufficient to split-off the hydrogen halide from the moleculewith the consequent production of olefin. However, for greaterconvenience and for the purpose of eliminating undesirable sidereactions, it is preferred to accomplish the dehydrohalogenation atrelatively low temperatures while enhancing the conversion rate byconducting the reaction in the presence of a suitable catalyst. A numberof `Such catalysts have been disclosed in the art such as metals, metalsalts, and other composites containing refractories, clays, alloys, andthe like. Although many of these methods of dehydrochlorination can beemployed to accomplish the desired function in the process of thisinvention, it is presently preferred that the dehydrochlorination beconducted in the presence of high surface oxidized carbon or pelleteddiatomite in conjunction with a ceramic binder at a ternperature in therange of from about 750 to about 850 F. In one embodimentthe efiiuentfrom the dehydrochlorination operation comprising HCl, terminal olefin,internal olefin and possibly some unconverted halogenated hydrocanbon isfractionated to remove HC1 from the system, to yrecover terminal olefinas product and unconverted halogenated hydrocarbon as recycle to thedehydrochlorination operation. In this embodiment the internal olefinsrecovered in such fractionation operations are passed to a subsequentisomerization operation wherein they are converted to the desired1o1efin.

In practicing the isomerization operation employed in the process ofthis invention, it can be any one of numerous methods that have beenfound effective for converting :internal olefins to terminal olefins andVice versa. The isomerization -of olefins is a well known phenomena. Thedouble bond present in olefinic hydrocarbons is rather labile and,accordingly, it can be caused to shift under suitable conditions.

Methods well known in the art, however, have generally required that theisomerization of the olefinic unsaturation to the terminal positionrequires rather high temperatures to accomplish any substantial degreeof conversion. Such high reaction temperatures, generally in excess of700 F., result in undesirable thermodecomposition of feed and productsalike with the consequent production of coke and gaseous by-productswhich undesirably affect the overall operation and particularly theisomerization yield. It is, therefore, preferred in one embodiment ofthe present invention to employ as the isomerization step,

a mode of operation that does not require the excessively hightemperatures that result in the above-described disadvantages. Thepresently preferred mode of isomerization is thehydroboration-displacement technique described by H. C. Brown and G.Zweifel, Journal of American Chemical Society, 82, 1504, 1960.Generally, this technique involves the reaction of hydrogenboride withthe internal olefin to produce the corresponding trialkylborane which isisomerized at from about C. to about 175 C. to produce the correspondingterminal boronalkyl. This terminal alkyl is then contacted withdisplacement l-olefin used in excess in the league of C. to displace theboron from the alkyl radical with the consequent production of thedesired terminal olefin.

When the production of internal olefins is preferred, another mode ofisomerization is desirable. In this iustance the l-olefin can becontacted with a clay isomerization of which numerous variations areknown in the art. For example, suitable catalysts are those disclosed inU.`S. 2,613,233. Such isomerization is usually conducted in a packedcolumn, the packing of which may be the isomerization catalyst orsuitable refractory' or other column packing impregnated with thecatalyst. Catalysts which are suitable for this purpose are Floridin,kaolin, diatomaceous earth, bauxite, activated alumina, silica gel, orthe like, or the same materials or inert support material such aspumice, impregnated with a slight amount of acid, such as sulfuric orphosphoric, or with acidic sulfate, phosphate, uoride, or like salts ofthe alkali, alkaline earth, or other inorganic elements.

A more complete understanding of the concept of the present inventioncan be obtained by reference to the attached drawings which show inschematic form the several features of photochlorination,dehydrochlorination, and isomerization as well as the required andpreferred fractionation, recycle, and recovery facilities.

In the drawings, FIGURE 1 is a schematic of apparatus suitable foreffecting the concept of this invention, including hydroborationdisplacement. FIGURE 2 illustrates a similar scheme wherein a simplerisomerization system is employed.

Referring now to FIGURE l, the hydrocarbon feed to be converted toolefin is passed by way of pipe 1 and cooler 3 to photochlorination zone4. Prior to its introduction into the photochlorination zone, thehydrocarbon feed is admixed with chlorine which is introduced by way ofpipe 2. The photochlorination can be conducted in several serial stagesas previously described or can be conducted in a single stage in thepresence of high concentrations of chlorine and high intensities ofultraviolet radiation depending upon the selectivity of conversion tomonochlorinated products desired. In the photochlorination zone, themixture of hydrocarbon and chlorine is subjected to ultravioletradiation from a suitable source 5 having a wave length of from about2500 A. to about 6000 A. at a temperature of from about 40 to about 280F. for a reaction time of from about 5 to about 25 seconds in eachreactor where one or more stages are employed.

In such operations the preferred hydrocarbon feedstock is a normalalkane having from about 7 to about 15 carbon atoms per molecule inwhich case a pressure from about 40 to about 60 p.s.i.g. is required atchlorination conditions to maintain liquid phase. In the presentlypreferred mode of operation, the amount of chlorine added to thephotochlorination zone is that required to give the desired conversionof hydrocarbon. Under such conditions, the residence time of preferablyabout l5 seconds in each serial chlorination zone is sufficient toprovide for the conversion of substantially all of the halogen present.It should be pointed out that although a wide range of hydrocarbonfeedstocks can be employed in the concept of this invention it ispresently desirable for reasons of operability and product distributionto substantially limit the hydrocarbon feed to no more than two adjacenthomologues of the alkane series, and it is generally preferred to employa hydrocarbon feedstock comprising primarily only one member of thealltane series within the range above-noted.

The eiuent from the photochlorination zone comprising HCl, unconvertedhydrocarbon, monoand dichlorinated derivatives is passed by way of pipe6 and cooler 7 to fiash drum 8 wherein the HC1 is removed as overhead byway of pipe 9 and vented from the system. The remaining hydrocarbonphase having therein only a negligible amount of HC1 is removed by wayof pipe 10 and passed to fractionation column 11 wherein unreactedhydrocarbon is removed as overhead product by way of pipe 12 andrecycled into admixture with the fresh feed to the photochlorinationzone. Bottoms product comprising primarily chlorinated hydrocarbons ispassed by way of pipe 13 to distillation column 14 wherein themonochlorinated derivatives are removed as overhead by way of pipe 15and more highly halogenated derivatives are removed from the system byway of pipe 16. The monohalogenated derivatives are passed by way ofpipe 15 to dehydrochlorination zone 17 wherein they are contacted with asuitable dehydrochlorination catalyst at a temperature of from about 750to about 850 F. The catalyst employed in this operation can be any thatwill achieve a substantial degree of conversion to the desired products,and in the presently preferred embodiment of this invention eitheroxidized carbon or diatomite in conjunction with a ceramic binder can beemployed. Where diatomite is employed, it has been found advantageous totreat the catalyst material before its introduction to thedehydrochlorination zone with a l percent aqueous solution of potassiumhydroxide. Where dodecane is employed as the hydrocarbon feed to thephotochlorination zone and the liquid hourly space velocity in thedehydrochlorination zone is maintained in the range from about 0.5 toabout 2.0 the conversion of rnonohalogenated derivative to thecorresponding olefin is in the range of about 95 to about 99 percentwith a selectivity to n-dodecane-l of about 95 to about 99 percent.

The effluent from the dehydrochlorination zone comprising HC1, l-olefin,and internal olefins is passed by way of pipe 18 and cooler 19 to asuitable flash vessel 20 wherein HCl is removed as overhead through pipe21 and vented from the system. The remaining hydrocarbon phasecomprising primarily olelinic hydrocarbon is removed by way of pipe 22and can be admixed, in one embodiment, with recycle internal olefin fromthe isomerization zone hereinafter detailed. In this embodiment themixed feed is introduced to a suitable fractionation Zone 24 whereinterminal olefin product is removed as overhead by way of pipe 25 andinternal olefin along with a small amount of high molecular weightmaterial produced in the dehydrochlorination zone is removed as bottomsproduct by way of pipe 26. This mixture is further fractionated in asuitable fractionation zone 27 wherein internal olefin is removed asoverhead product and relatively high molecular weight materials areremoved from the system by way of pipe 29.

The internal olefins are passed by way of pipe 28 to a suitable stirredreactor 30 wherein they are contacted with a solution of diborane indiglyme, which is the dimethylether of diethylene glycol, supplied tothe reactor by way of pipe 31. In the presently preferred embodiment ofthis invention, a reaction time of about 30 seconds at 20 C. is employedin reactor 30 to effect the production of the desired borane derivative.This derivative is then passed by way of pipe 34 to a suitablefractionator 35 which in this embodiment comprises fractionaldistillation apparatus operated under heavy reflux at a preferredtemperature of 180 C. for an average residence time of from about l toabout 3 hours in order to effect 4the isomerization of the internalolefin to l-olen. Propylene, in an amount in excess of thestoichiometric quantity required to displace the olefin presen-t incolumn 35, is passed from accumulator 36 via pipe 37 as controlled bysuitable valve means 38 into admixture with the borane derivative fromstirred reactor 30 and is then passed to column 35 to displace thel-dodecene. The l-dodecene thus displaced and the excess propylenepresent in column 35 are passed as overhead by way of pipe 32 whilepropylene borane is removed as kettle product from column 35 by way ofpipe 39 and is introduced to column 40. A part of the internal olefinspassing through pipe 28, sufficient to displace propylene from thepropylene borane, is passed by way of pipe 41 into admixture with thepropylene borane in Column 40. rl`he propylene thus displaced isrecovered as overhead product from fractionator 40 and is passed by wayof pipe 42 to accumulator 36. In the presently preferred embodiment ofthis invention, the average residence time of the latter describeddisplacement step effected in column 40 is about 1 hour. Similar to theoperation of column 35, column 40 is also operated under heavy reflux inthe presently preferred mode of operation. Bottoms product from column40, comprising tridodecylborane and diglyme is recycled to isomerizationcolumn 35 by way of pipe 43. The overhead product from column 35,comprising l-dodecene product and excess propylene, is passed by way ofpipe 32 to fractionator column 44, in which the propylene and l-dodeceneare separated; the propylene being recovered as overhead product andpassed by way of line 45 to accumulator 36, and product ldodecene beingrecovered as bottoms product by way of pipe 47. Make-up propylene issupplied to accumulator 36 by way of pipe 46 to accommodate for lossesin the operation.

The hydroooration is preferably carried out in the presence of 10 to 20percent excess hydride to insure the quantitative utilization of olefin.The use of a suitable solvent such as diglyme (diethylene glycolmonomethyl ether) is preferred. However, the quantity of hydrideemployed can be varied as desired depending upon degree of conversion,residence time and reaction temperature. It has been found that theconversion of higer molecular weight internal olefins to thecorresponding terminal olefins is substantially slower than theconversion rates of relatively lower molecular weight compounds. It hasalso been found that the rate of conversion can be substantiallyincreased at higher temperatures in the range of 150 C. However, in thepresently preferred embodiment of this invention, the hydroborationreaction is carried out at a temperature from about to about 100 C. andfor a residence time of from about 1 to about 3 hours. Higher ultimateconversions are, of course, obtained with longer residence times andhigher concentrations of boronhydride. However, it has been found thatin the preferred range of operating conditions wherein internaldodecenes are employed as the olefin feed to hydroboration zone andreaction conditions are maintained at about C. and from about l to about3 p.s.i.g. with an excess boronhydride of about 20 percent that theyield of terminal olefin based on feed olefin is in the league of 98percent. Within the range of operating conditions noted, the ultimateconversions generally achieved are within the range of about 75 to about98 percent.

This boron displacement is accomplished in the presence of an excess ofterminal displacement olefin such as tetradecene-l which has been foundsuitable for this purpose wherein the boron alkyl is tridodecylboron.Preferably, because of ease of separation, propylene can be used as thedisplacement olefin. Theoretically, only a stoichiometric equivalent ofdisplacement olefin is required to achieve the desired conversion to thedesired terminal olefins. However, it has been found that the presenceof about l5 to about 25 molar excess displacement olefin in thedisplacement reactor `greatly enhances the conversion rate and ultimateyield. In one embodiment, as shown in the drawing, the displacementolefin can be admixed with the boron alkyl feed to the displacement zoneprior to the introduction of the thus-formed mixture into the reactor.However, suitable conversions can be obtained by introducing these twocomponents to the displacement zone as separate streams. It has beenfound that the rate of the displacement reaction is enhanced at highertemperatures and that suitable conversions can be achieved attemperatures within the range of from about 125 to about 175 C. However,in the presently preferred embodiment of this invention, whereindodecane is employed as the feed to the abovedescribed photochlorinationzone the temperature in the displacement zone is maintained in theleague of about 160 C. The pressure maintained during this operationneed only be that required to maintain liquid phase reaction. It hasalso been found advantageous to provide suitable means for agitating themixture during its residence in isomerization vessel 30. Residence timesin the displacement zone are generally in the range of 0.5 to about 3hours. However, it has been found that about 90 to about 95 percentconversion of tridodecylborane to terminal dodecene can be accomplishedin the presence of 1500 percent excess propylene at about 160 C. wherereaction is continued for a period of 2 hours.

Regeneration of the propylene used as displacement hydrocarbon is easilyaccomplished by contacting this boron alkyl with an equimolar quantityof internal C12 olefin. This step is shown in vessel 40. Approximatelyone hour is required. The propylene is removed overhead and returned topropylene storage vessel. The tridodecyl borane is recycled to theisomerization reactor vessel 35.

The operation of the above-described fractionation zones need only besuitable to accomplish the required separations. However, it ispreferred to maintain the pressure in both of these operations at arelatively low value generally in the range of atmospheric pressure orin an excess thereof for reasons that by such operation lowertemperatures are required to accomplish the desired separation. Theseconditions will, of course, vary depending upon the molecular weight ofthe feed hydrocarbon and displacement olefin, but it is generallypreferred to maintain the fractionation temperatures relatively low inorder to avoid any substantial decomposition of the boron alkyls.

Where it is preferred to produce internal olefins to the exclusion ofl-olefins, the internal olefin can be recovered from the fractionationzones following dehydrochlorination and the l-olefins can be passed to aconventional isomerization reactor and converted, at least in part, tointernal olefins after which unconverted terminal olefins are separatedand recycled to the isomerization reactor.

This alternate embodiment is illustrated in FIGURE 2 wherein 52 is apacked isomerization zone and 55 is a product fractionator. The vessels,sequence of operation and numbering of the photochlorination,intermediate fractionation and dehydrochlorination are as defined anddescribed for FIGURE l.' Terminal olefin is removed as overhead fromfractionator 24 and passed to isomerization zone 52 which is packed withsuitable isomerization catalyst 53 as above described. The isomerizationreactor is preferably operated within a temperature range of from about120 to about 150 F. to convert at least part of the terminal olefin tointernal olefin. The reaction product comprising a mixture of terminaland internal olefin is removed as overhead from isomerization zone viaconduit 54 and is passed to fractionation or stripping means 55.Relatively low molecular weight materials produced in isomerization areremoved from fractionator S as overhead by way of pipe 56. Heaviermaterials including the desired internal olefin and unconverted terminalolefin are removed as bottoms product by way of pipe 57 and recycled byway of pipe 23 as feed to fractionator 24.

As a result of such operations, the terminal olefin can be recycled toextinction thereby providing for the conversion of substantially all ofthe hydrocarbon feed to the desired internal olefin which is removed byway of pipe 51 from fractionator 27.

In producing internal olefins, as described immediately above, valves 58and 60 will be closed, and valves 59 and 61 will be open. However, it isalso possible to produce terminal olefins as the product and send thestream rich in internal olefins to the isomerization unit 52 forconversion, at least in part, to terminal olefins. In this latter case,terminal olefins will be removed as product from the overhead stream offractionator 24. For the production of terminal olefins, valves 58 and60 will be open, and valves 59 and 61 will be closed.

The aforegoing discussion and the attached drawings are only intended tobe illustrative of one embodiment of this invention and the applicationof the concept of this invention in one particular instance and are notintended to limit the scope or the application of the concept of thisinvention.

Reasonable variation and modification are possible within the scope ofthe foregoing disclosure, drawing and claims, the essence of which isthat there is provided a method and apparatus for converting hydrocarbonfeedstocks to the corresponding olefins which method comprisesphotochlorinating the hydrocarbon in the presence of an ultravioletlight, dehydrochlorinating the monochlorinated hydrocarbons thusproduced and subsequently isomerizing either the internal or terminalmonoolefins produced in the dehydrochlorination operation to yield thedesired olefin product.

I claim:

ll. A method for producing selected monooleiins from saturated alicyclichydrocarbons having from 7 to 15 carbon atoms per molecule whichcomprises photochlorinating said hydrocarbon in the presence of chlorineand ultraviolet radiation having a wave length of from about 2500 toabout 6000 Angstroms at a temperature of from about 40 to about 230 F.to produce monochlorinated hydrocarbons containing some HCl, unreactedhydrocarbon, monochlorinated and dichlorinated hydrocarbons,fractionating this photochlorination efiiuent mixture in a firstfractionation zone to separate said HCl as overhead, fractionating thebottoms product from said first fractionation zone comprising unreactedhydrocarbon, monochlorinated and dichlorinated hydrocarbons in a secondfractionation zone to produce a second overhead comprising primarilysaid unconverted hydrocarbon thereby separating said unconvertedhydrocarbon from said monochlorinated and dichlorinated hydrocarbons,fractionating the mixture of monochlorinated and dichlorinatedhydrocarbons having substantially reduced concentration of saidunconverted hydrocarbon to recover said monochlorinated hydrocarbon asoverhead and said dichlorinated hydrocarbon as bottoms product,recycling said unconverted hydrocarbon as feed to said photochlorinationstep, dehydrochlorinating said monochlorinated hydrocarbon in adehydrochlorination zone in the presence of a basic catalyst at atemperature of from about 750 to about 850 F. and a pressure of fromabout 40 to about 60 p.s.i.g. to convert said monochlorinatedhydrocarbon to olefin hydrocarbons, fractionating the effluent from saidydehydrochlorination zone comprising olefin, chlorinated hydrocarbon,HC1, terminal and internal olefins to produce a bottoms productcomprising primarily said chlorinated hydrocarbon and recycling saidchlorinated hydrocarbon as Ifeed to said dehydrochlorination zone.

2. The method of claim 1 wherein the efiiuent from saidphotochlorination is flashed to remove HCl as overhead, the remainder isfractionated to produce unconverted hydrocarbon as overhead andchlorinated hydrocarbon as bottoms product, said unconverted hydrocarbonoverhead is passed as recycle to said photochlorination, saidchlorinated hydrocarbon bottoms product is fractionated to separatemonochlorinated hydrocarbon as overhead and dichlorinated hydrocarbon asbottoms product, the efiiuent from said dehydrochlorination is fiashedto remove HCl as overhead, the remainder comprising terminal andinternal olefins is fractionated to recover said terminal olefin asoverhead and internal olefins as bottoms product and wherein saidhydrocarbon comprises primarily two adjacent homologs of the alkaneseries having from about 7 to about 15 carbon atoms per molecule.

3. The method of claim 1 wherein said hydrocarbon has from about 7 toabout 15 carbon atoms per molecule, said photochlorination is effectedin the presence of chlorine and ultraviolet radiation having a wavelength of from about 2500 to about 6000 Angstroms at a temperature offrom about 40 to about 230 F. to produce monochlorinated hydrocarbon,the product from said photochlrination comprising HCl, unreactedhydrocarbon, monochlorinated and dichlorinated hydrocarbon isfractionated to separate and recover said uncon-verted hydrocarbon andsaid monochlorinated hydrocarbon, said unconverted hydrocarbon isrecycled to said photochlorination step, said -monochlorinatedhydrocarbon is passed -as feed to said dehydrochlorination step, saiddehydrochlorination is effected in the presence of a basic catalyst at atemperature of from about 750 to about 850 F. and a pressure of fromabout 40 to about 60 p.s.i.g. to convert chlorinated hydrocarbon toolefin, the product from said dehydrochlorination step comprisingchlorinated hydrocarbon, HC1, terminal and internal olefin isfractionated to separate chlorinated hydrocarbon for recycle to saiddehydrochlorination, internal olefin as product, and terminal olefin,said terminal olefin is passed as feed to said isomerization operationto convert at least a portion of said terminal olefin to internalolefin, the isomerization product from said isonierization operationcomprising internal and terminal olefin is fractionated to recover saidinternal olefin as product and said terminal olen is recycled to saidisomerization operation and wherein said hydrocarbon comprises primarilytwo adjacent homologs of the alkane series having from about 7 to about15 carbon atoms per molecule.

References Cited UNITED STATES PATENTS OTHER REFERENCES Herbert C. Brownet al.: J. Amer. Chem. Soc., vol. 82, pp. 1504-5, 1960.

DELBERT E. GANTZ, Primary Examiner.

V. OKEEFE, Assistant Examiner.

